So I worked midnight to 8am shifts while UG to pay for school. I obviously want the admissions office to notice this, and working 30 hours a week while in school had an obvious effect on my GPA. Where is the best place to put this?

I'm certainly no expert, but I think this is a perfect justification for a GPA addendum. Just make the tone neutral and fact-based. Also, you should definitely put the job on your resume, and many schools ask for employment stuff on the app itself.